Welcome to this edition of the IAAI’s CFITrainer.Net podcast. Today we are going to dig into a topic making news right now, the cause of spontaneous fires in electric cars. A little background first. We covered fires in hybrid vehicles on this podcast back in 2009. Obviously, in the ten years since, a lot has changed. Now, we are talking more and more about fully electric vehicles and the challenges they pose for fire suppression and fire investigation. Although plug-in electric cars are only about 2% of the vehicles on the road right now, which is about 5.6 million cars worldwide, the forecast is staggering. According to the International Energy Agency, by 2030, there will be 125 million electric cars on the road. Growth year over year is astonishing — from last year to this year, the number of electric cars on the road increased 64%. Fire investigators are going to be seeing more and more electric vehicles involved in vehicle fires, so now is the time to get out ahead of this trend with better awareness and training in electric vehicle fires.

A pretty simple Google search will turn up multiple incidents of fires in electric cars, some starting after a crash and some spontaneous with seemingly no precipitating event. Recently, the coverage has been about spontaneous fires that have started in Tesla models, some of which were plugged in and charging and some of which were parked and not charging. These incidents have taken place in societies as diverse as the US, Hong Kong, and China. In incidents not related to crashes, the most common cause identified to date appears to be the lithium ion battery and/or the charging process. Government has begun to get involved. China, the world’s biggest market for electric cars, recently ordered electric vehicle manufacturers to check their vehicles for problems with batteries, waterproof protection, wire harnesses, and charging devices. Industry has also begun reacting with extreme caution; In June, Audi recalled its first all-electric vehicle sold in the U.S over concerns about battery fires. E-Tron SUVs have also been recalled over fears that a problem with the wiring harness can allow moisture to get into the battery, thus potentially causing a fire.

From the perspective of the fire investigator, what is important here is to ask how we can be aware of potential fire causes in an electric vehicle and how we can obtain training to investigate those potential fire causes. Business Insider reviewed Tesla fire incidents and found that most fires seemed to be caused by assault to the vehicle’s battery, typically from a high speed crash. When a battery is damaged, it can go into “thermal runaway,” where the temperature in one cell rapidly increases, causing the temperature in another cell to rapidly increase, and so on in a chain reaction. In some cases, this process self-arrests before a fire occurs. In others, it continues until the ignition temperature of the materials is reached and open flaming combustion occurs. Thermal runaway incidents have been reported in multiple electric and hybrid vehicles, including the Zotye M300 EV, Chevrolet Volt, Fisker Karma, Dodge Ram 1500 Plug-in Hybrid, Toyota Prius Plug-in Hybrid, Mitsubishi i-MiEV and Outlander P-HEV.

But what about the fire cases where the electric vehicle was parked, either charging or not charging. What caused those fires? There are many possibilities to consider in an investigation.

In the Business Insider article, Brock Archer, an auto-extrication expert, states that lithium ion battery fires are most commonly caused by liquid, dead short, or spontaneous combustion. Of those three, spontaneous combustion is a rare event, one battery cell in a billion. But, each electric car battery contains thousands of cells, so, with millions of those batteries on the road, spontaneous combustion is definitely a possibility. Most of these stationary electric vehicle fires occurred while the vehicle was charging or fully charged, leading Tesla to recently release a software update to change how the charging process and intensity are managed. So, the charging process itself may also be a contributing cause.

Further, Business Insider notes that manufacturing defects are possible. In September 2018, there was an oil spill in the Panasonic portion of Tesla's Gigafactory. Mechanical oil from a manufacturing machine that presses battery chemicals into a sheet got into the finished sheets. Millions of finished cells had to be examined for contamination. Even tiny fragments of metal getting into the battery chemicals during manufacturing could later cause a short or a fire in the finished battery installed in a vehicle.

A report by the National Highway Transportation Safety Administration that assessed potential lithium-ion battery vehicle safety issues identified another cause that may be at play in electric vehicle fires that seem to occur without any precipitating event. The report found that, “Li-ion failure processes may be understood as electrochemical or stress induced ‘damage’ at the cell level that incubates, initiates, and grows until failure. Li-ion failure processes are time-dependent process. While failure can sometimes occur very rapidly after a cell is damaged, damage may also sometimes grow over many years and many duty cycles, causing delayed failure long after damage is initiated.” This means that a vehicle battery that was previously damaged might not cause a fire immediately; the damage may grow over extended periods of time and later result in a fire that seems unconnected to the damaging event that occurred a long time ago. And, the damage may not even be dramatic, like a crash. The report further explains, “For each battery chemistry, design, and expected duty cycle, there is a range of temperatures and range of operating voltage in which electrochemistry is dominated by intercalation mechanisms. Outside this range, undesirable side reactions may occur which can lead to self-heating (exothermic reactions) and/or internal electrical shorts (excessive flow of electrons). Exothermic reactions and/or internal electrical shorts may be triggered by manufacturing defects, or mechanical, electrical, or thermal errors, misuse or abuse. If allowed to continue, these reactions or shorts can create conditions for self-heating within the cell; which grow to become uncontrolled increases in temperature and pressure (thermal runaway); and potentially end in venting or catastrophic failure of the cell.”

At this time, as the body of data on electric vehicle fire causes continues to build, it is important that all reasonable accidental causes are examined through the scientific method. And, reporting findings is critical to building the data that will help us better understand electric vehicle fire causes and spur industry to address and eliminate those causes.

One more note on a fact can make fires that involve an electric car battery more difficult to investigate. A lithium ion battery fire cannot be extinguished with foam or dry chemicals. Only very large volumes of water over a sustained period of time can put it out. Because of the long burning time, damage can be extensive and thus investigation more difficult. And, it must be noted, even extinguishing an electric car battery fire is no guarantee another fire will not occur. In February 2019, a Tesla caught fire in a Pittsburgh residential garage. The fire was extinguished and the vehicle transported to a vehicle shop for further investigation. The vehicle caught fire again only hours after arriving at the shop.

Thank you for being with us today. Electric vehicle fires is, frankly, a big topic and we’ve just scratched the surface here of what a fire investigator needs to be thinking about when working an electric vehicle fire. We encourage you to continue to seek out resources to educate yourself on electric vehicle fire causes and to put this topic on your list of emerging issues you want to keep current on. This podcast’s page has links to some news articles and resources to get you started.

A little bit of news from the IAAI.

We want to say congratulations to the Nebraska Chapter for quite a milestone fifty years, with the IAAI. You go Nebraska! Nebraska shows 426 users on CFITrainer.Net and there are four listed CFI’s that are showing up here on CFITrainer.Net.

As always check out the FireArson.com website for information of upcoming training around the globe. Classes are added on a regular basis and while you’re there save some money on your registration for ITC coming next April 26th thru May 1st in Las Vegas at Planet Hollywood. To learn more about ITC, go to www.IAAIITC.com, for a site dedicated to our premier annual training and networking event. Those who register early save one hundred dollars. At least go over to the site and begin to make your plans. There is still some time to get in on the early bird special.

Thanks for joining us today on this podcast. Stay cool and stay safe out there and we’ll see you next time on CFITrainer.Net.

For the International Association of Arson Investigators and CFITrainer.Net, I’m Rod Ammon.